Download Yeast Infection of the Skin.vp

Yeast Infection of the Skin
YEAST DERMATITIS
(MALASSEZIA INFECTION)
Yeasts are the spore-like forms of fungi (as shown in the photomicrograph on the right).
Malassezia dermatitis is a fungal infection of the skin by the Malassezia fungus..
WHY SUSPECT YEAST?
Yeast infections are especially itchy, crusty, and
smelly. Often a dog starts with a rash or with simple
itching but the skin thickens to an “elephant” skin
appearance. The itch is extreme and the odor can
be especially troublesome. Parts of the body or the
entire body can be affected. Malassezia overgrowth
is particularly problematic where there are skin
folds ("armpits," eyelids, facial folds, lip folds, throat
latch, and especially between the toes). Mostly
dogs are affected but cats can get yeast infections
as well.
The dark footprint-like structures
seen here are the yeast organisms:
Malassezia pachydermatis
WHERE WOULD A DOG GET A YEAST INFECTION?
Yeast happily live on most normal skin as well as in ears
and anal glands. To get a yeast infection, conditions on
the skin surface have to change to favor the proliferation of
the yeasts. The yeasts in small normal numbers are
harmless but when the yeasts are present in large
numbers, disease results.
So what conditions lead to a yeast proliferation? An
increase in skin oils (which often occurs in an allergic flare
Note the "elephant skin"
up) would be the most common situation. Sometimes there
appearance
that is especially
is an immune deficiency or hormone imbalance which
common with Malassezia
allows for the yeast proliferation. Some animals are battling
dermatitis. The more scientific
seborrhea (excessive oil production of the skin) and thus
term for this finding is
are naturally predisposed to the yeast proliferation. The
"lichenification."
most important thing to realize is that while a yeast infection
is not contagious, it tends to recur unless
the underlying allergy, seborrhea, or other
problem is controlled. The yeast overgrowth
is extremely itchy and if it can be controlled,
the underlying allergy, seborrhea etc. may
not be all that itchy in and of itself.
This dog's skin also shows lichenification along with redness from active inflammation.
– Page 1 of 3 –
The following breeds are predisposed genetically to yeast infections: the West
Highland White Terrier, Basset hound, Cocker spaniel, Silky terrier, Australian terrier,
Maltese, Chihuahua, Poodle, Shetland sheepdog, Lhasa apso, and the Dachshund.
HOW IS THIS CONFIRMED?
There are several testing methods to confirm the overgrowth
of yeasts:
• Impression smear (pressing a microscope slide on the
skin to collect yeast organisms)
• Scotch tape sampling (pressing a piece of clear tape to
the skin to collect yeast organisms)
• Skin scraping with a blade (scraping the skin with a
blade to collect yeast organisms)
• Cotton swab (rubbing a moistened Q-tip on the skin to collect yeast organisms)
• Skin Biopsy (removing a small plug of skin with a biopsy punch with a local
anesthetic. This is the most invasive choice but provides substantially more
diagnostic information)
Very few yeasts need to be seen under the microscope to confirm yeast infection.
A special situation is worth mentioning: Malassezia hypersensitivity. In this situation, the
patient actually becomes allergic to the fungus so that very small numbers of organism
on the skin generate an extreme itch reaction. This scenario is confirmed by an
injection test where an extract of yeast is injected into the skin and the swelling is
compared to swelling generated by histamine (a very inflammatory positive control)
and to that generated by saline (a completely non-inflammatory negative control).
Animals that are hypersensitive to yeast in this way will need allergen specific
immunotherapy (allergy shots) to reduce their sensitivity.
HOW DO WE GET RID OF IT?
Treatment can be topical, oral, or both. Topical treatment is best used for localized
spots of infection while oral medication would be better applied to larger infected areas.
If the yeast infection is recurrent or if one wishes to supplement oral medication, topical
and oral treatment can be combined.
Oral therapy: Ketoconazole and its derivatives (the so-called "azole" class of
antifungal drugs) rule when it comes to oral therapy. Typically a several week treatment
is needed and there are numerous protocols involving different dosing schedules.
Higher doses tend to be needed if recurrence is a problem. The extreme itch usually
improves or resolves within one week. For animals that do not tolerate the azole class
of medications, terbinafine is a good alternative choice.
– Page 2 of 3 –
Shampoos: While degreasing shampoos such as the benzoyl peroxide (Oxydex®,
Pyoben®) and sulfur/salicylate (Sebolyt®, Sebolux®) shampoos will help remove the
skin oils feeding the yeast, there are shampoos that are specifically anti-yeast. We
prefer the 4% chlorhexidine shampoo called Chlorhexiderm Max® or Malaseb®
shampoo as these both strip skin oil and kill yeast; however, other anti-yeast products
include Selsun Blue®, Miconazole® shampoo, Nizoral® shampoo, Douxo® shampoo
and more. The pet must be bathed twice a week to start and the shampoo requires a
15 minute contact time (meaning do not rinse the lather for 15 minutes).
Spot Treatments: If only a small area is involved, it is probably not necessary to
bathe the entire animal. Special acetic acid wipes can be used to cleanse the affected
area. Mixtures of vinegar and water can be used but the pet will develop a distinct
vinegar odor. A newer product called Douxo® made by Sogeval is available as a
spot-on, topical liquid, or spray.
Treatment of the Underlying Cause: It is important to realize that yeast
overgrowth occurs in response to a primary problem be it allergy, seborrhea or
something else. If the underlying problem is not controlled, yeast dermatitis is likely to
periodically recur. It is common for allergic dogs to require some kind of periodic if not
on-going anti-yeast therapy.
Mar Vista Animal Medical Center
3850 Grand View Blvd., Los Angeles, CA 90066 l (310) 391-6741 l Fax: (310) 391-6744
Information on additional pet care topics can be found on our world wide web site:
http://www.marvistavet.com